Use of long chain alcohols, ketones and organic acids as tracers

ABSTRACT

Non-halogenated molecules having from 10 to 30 carbon atoms selected from the group consisting of aliphatic, aromatic, saturated, unsaturated (and combinations thereof) alcohols, ketones, organic acids, organic acid salts, sulfonated derivatives of these compounds, and combinations thereof are used as tracers to measure oil and/or water fluid returns, such as from a hydraulic fracturing job. The non-halogenated molecules may be absorbed onto and/or adsorbed onto substrates and introduced into a subterranean location, desorbed and recovered from the subterranean location with a fluid, reacted with a reagent (e.g. pentafluoro benzyl chloride, and the like) to give a derivatized tracer. The presence of the derivatized tracer is then detected in at least a portion of the recovered fluid. A different non-halogenated tracer may be used for each hydraulic fracturing stage, thus, it can be determined from which fracturing stage water is produced and from which fracturing stage oil is produced, for example.

TECHNICAL FIELD

The present invention relates to methods and compositions fordetermining from which fracturing stage a particular fluid is producedin a multi-stage hydraulic fracturing operation, and more particularlyrelates to methods and compositions for determining from whichfracturing stage a particular fluid is produced in a multi-stagehydraulic fracturing operation which does not use halogenated tracers.

TECHNICAL BACKGROUND

It is well known that hydrocarbons (oil and gas) are produced from wellsdrilled in the earth, hereinafter referred to as “oil wells.” It isadditionally well known that drilling a hole into the earth to reach oiland gas bearing formations is an expensive operation which limits thenumber of wells that can be economically drilled. It follows then thatit is desirable to maximize both the overall recovery of hydrocarbonsheld in the formation and the rate of flow from the subsurface formationto the surface, where it can be recovered.

One way in which to maximize production is the process known ashydraulic fracturing. Hydraulic fracturing involves cracking orfracturing a portion of the hydrocarbon-bearing formation surrounding anoil well by injecting a specialized fluid into the wellbore directed atthe face of the geologic formation at pressures sufficient to initiateand/or extend a fracture in the formation. Ideally, what this processcreates is not a single fracture, but a fracture zone, that is, acomplex zone having multiple fractures, or cracks in the formation,through which hydrocarbon can more readily flow to the wellbore.Proppants and other materials are pumped into the fractures or cracks tokeep the fracture open once the hydraulic pressure is released. Suchpropped fractures have increased permeability compared to thesurrounding rock, which improved permeability facilitates the productionof hydrocarbons. The proppants or other materials may contain substrateparticles such as diatomaceous earth (DE) that may have treatingmaterials adsorbed or otherwise contained on the substrate. Thesetreating materials may include, but not necessarily be limited to scaleinhibitors, paraffin inhibitors, corrosion inhibitors, and the like,which may desorb from the substrate particles to treat the producedhydrocarbons.

Fracturing fluids can vary widely in composition. Slick water is waterto which has been added chemicals to increase its fluid flow, notablyfriction reducers such as a polyacrylamide. Friction reducers improvethe ability of the fluid to be pumped under pressure to cause fracturingand with less power than essentially only water. Other optionalcomponents include biocides, corrosion inhibitors, scale inhibitors andthe like. Fracturing fluids may also comprise water that has beenviscosified, such as by using a crosslinked or non-crosslinkedpolysaccharide such as guar gum or the like, and/or by using aviscoelastic surfactant (VES) such as an amidoamine oxide.

Creating a fracture in a hydrocarbon-bearing formation requires severalmaterials. Often these materials, if not removed from the oil well, cansubsequently interfere with oil and gas production. Even the drillingmud used to lubricate a drill bit during the drilling of an oil well caninterfere with oil and gas production. Taking too long to remove suchmaterials can increase the cost to the operator of the well by delayingproduction and causing excess removal expenses. Not being thorough inremoving such materials can increase the cost to the operator of thewell through lower production rates and possible lost production.

Measures taken to remove unwanted or unneeded materials are usuallyinexact. Sometimes additional fluids are used to flush out unwantedmaterials in the well bore. In other situations, reservoir fluids flowcan make estimating return flow very difficult, particularly if thereservoir fluids are incompatible with the injected materials. It wouldbe desirable in the art of oil and gas production to be able todetermine how much of a given material is left in an oil well after adrilling, fracturing or any other operation requiring the injection ofmaterials into an oil well. Tracers included in the material are a knownway of determining the presence, and sometimes the amount, of a givenmaterial remaining in or retrieved from an oil well with which thetracers are associated.

One hydraulic fracturing technique uses multiple fracturing stages wheredifferent isolated zones are fractured in different way designed orcustomized for each zone. However, once the well is placed intoproduction, and the fluids from all zones are produced together, itgenerally cannot be determined from which zone a particular portion ofthe fluid was produced since the fluids are intermingled. In the past,unique halogenated tracers have been injected into each of therespective zones, and by means of distinguishing the produced tracersand their associated fluids, it may be determined what types of fluids(and their compositions) are produced from which zones. Further, thetracers may help maximize the production of oil and gas. If it isdetermined that water is overwhelmingly produced from one particularzone, that zone could be isolated and shut off from production so thatless overall water is produced and the hydrocarbon production may bemaximized.

In the past, perfluorinated compounds have been used as tracers tomeasure oil returns from a fracturing job. These compounds have a oneparticular key advantage and many disadvantages. Their main advantage isthey are easy to detect. However, they are very expensive, and further,separating one compound from another is very difficult. Also,halogenated compounds remaining in the produced fluids will poison thecatalyst in the downstream refineries.

It would be particularly desirable if these goals could be achievedusing inexpensive tracers which are easily distinguished from oneanother.

SUMMARY

There is provided, in one non-limiting form, a method for determiningthe presence of a tracer from a subterranean location, which methodincludes introducing at least one non-halogenated tracer into asubterranean location, where the at least one non-halogenated tracer isa molecule having from 10 to 30 carbon atoms selected from the groupconsisting of alcohols, ketones, organic acids, and combinationsthereof, where the alcohols, ketones, organic acids and organic acidsalts may be saturated, unsaturated, aliphatic, and/or aromatic; thesetracers may also be sulfonated to help make them water soluble. Thenon-halogenated tracers are absorbed into and/or adsorbed onto aplurality of substrates. The method additionally comprises recovering afluid from the subterranean location where the fluid comprises the atleast one non-halogenated tracer that has desorbed from the substrate,where a majority of the plurality of the substrates remains within thesubterranean location. The method further involves reacting the at leastone non-halogenated tracer in the laboratory with a reagent to give atleast one derivatized tracer, and then detecting the at least onederivatized tracer from at least a portion of the recovered fluid.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph of the returns of a 2% solution of five halogenatedtracers from TRACERCO on diatomaceous earth (DE) demonstrating that thehalogenated tracers come off the DE immediately; and

FIG. 2 is a graph presenting data generated from a 1% loading ofalcohols on DE (half as much as in FIG. 1) demonstrating that thealcohols come off the DE much slower and in a more predictable mannerfor a longer period of time.

DETAILED DESCRIPTION

It has been discovered that a tracer detection method may be implementedusing non-halogenated long chain (in a non-limiting example, moleculeshaving from 10 to 30 carbon atoms) alcohols, ketones and/or organicacids as tracers and halogenated derivatives of the non-halogenatedmolecules in a laboratory for easy detection and separation. Advantagesof the method described herein include that the non-halogenated tracersare relatively inexpensive and are readily available. They are alsoeasily separated with a gas chromatograph equipped with an electroncapture detector (ECD) and detected at very low levels. However, it willbe appreciated that the method is not limited to GC/ECD; any othersuitable technique may be used. The method described herein may also beperformed with much more expensive equipment such as a gas chromatographwith a mass spectrometer (GC/MS) in selective ion monitoring mode (SIM)or in negative chemical ionization mode. The method herein may also bepracticed using high performance liquid chromatograph with a massspectrometer (HPLC/MS) with negative electro spray. There are likelyother methods of detection; however GC/ECD is expected to be one of themost economical.

More specifically, the method herein involves the analysis of long chainalcohols, ketones and organic acids as their derivatives to measure oiland/or water returns in produced wells, such as from a hydraulicfracturing operation. The alcohols, ketones, organic acids, and organicacid salts may be aliphatic, aromatic, saturated, unsaturated, and/orcombinations thereof, and may have from 10 to 30 carbon atoms;alternatively from 10 to 18 carbon atoms. The organic acid salts arealkali metal or alkaline earth metal salts, including, but notnecessarily limited to sodium, potassium and calcium salts of theorganic acids. The salts of the acids are water soluble and can beextracted from the water to determine where the water comes from. Alsopossible to be used as tracers are sulfonated alcohols, ketones, acids,and acid salts as water soluble compounds.

The non-halogenated tracers are introduced into one or more subterraneanlocation absorbed into and/or adsorbed onto a plurality of poroussubstrates. The tracers should remain absorbed into and/or adsorbed ontothe substrate for a period of time sufficient for the substrate to beplaced within a desired location, such as within a particular fracturecomplex, before the tracer begins to desorb from the substrate. That is,the tracer should not immediately desorb from the substrate, otherwiseit will not function suitably as a tracer. It has been discovered thatthe non-halogenated tracers “stick” or remain absorbed into thesubstrates more readily than halogenated tracers, the latter which werefound to quickly desorb. The alcohols, ketones, organic acids, organicacid salts and sulfonated derivatives thereof behave more likehydrocarbons or water; and in particular the organic acid salts and thesulfonated derivatives behave more like water. Thus, the non-halogenatedderivatives adhere or absorb into the substrates easily and are slow todesorb. In one non-limiting example, the tracer should remainsubstantially absorbed into the substrate within a time period of about24 independently to about 250 hours; alternatively from about 24independently to about 50 hours. Alternatively, the method may beunderstood as dependent on the volume of liquid produced from theformation. In a non-limiting instance, it is desirable that thenon-halogenated tracers recovered are detectable for at least 100 porevolumes of the induced fracture or more.

Suitable porous materials for the substrates include, but are notnecessarily limited to, diatomaceous earth (DE), alumina, absorbentresinous materials or polymers, porous ceramic beads, walnut shellfragments, nut shells, silica particulate, precipitated silica,activated carbon, zeolite, fullers earth, organic synthetic highmolecular weight water-insoluble adsorbants, and combinations thereof.In one non-limiting embodiment, the substrate may be a proppant. Some ofthese water-insoluble absorbents are further described in U.S. Pat. Nos.7,493,955 and 7,491,682, which are incorporated herein by reference intheir entirety. It is well known that as a hydraulic fracturing fluid ispumped against and into the formation, the fluid may fracture theformation, thereby increasing its permeability and stimulatingproduction. Proppants are used in the fluid to keep the fracture openafter the procedure has been completed. As the fluid pressure is removedand the formation relaxes, the proppants keep the fracture open andincrease permeability. The proppants and other porous media, such as thesubstrates, are thus disposed within and remain in fractures (or othersubterranean structure). To summarize, the substrates may be differentfrom, or the same as, the proppant used.

Proppants and substrates may have an average particle size of from about125 independently to about 1700 microns. Common ranges for proppantaverage particle sizes in methods including frac packing and gravelpacking include, but are not necessarily limited to, 12/18 mesh (about1680 independently to about 1000 microns); 20/40 mesh (about 841independently to about 400 microns); 30/50 mesh (about 595 independentlyto about 297 microns); 40/70 mesh (about 400 independently to about 210microns); 100 mesh (149 microns) and in some instances below about 100mesh (149 microns) as needed for certain applications.

The substrates may be beads or spheres that will take more closurepressure (the pressure exerted by the formation on the fracture toclose) than DE, but such beads would need to be coated with a material,such as an outer shell, that slowly dissolves with time and temperature,thereby allowing the non-halogenated tracer to desorb slowly. Suchsuitable coatings or shell materials include, but are not necessarilylimited to, polyvinylidene chlorides. The rate of desorption may becontrolled by the nature of the coating or shell, the thickness of thecoating or shell, and the fluids that will contact the coating or shellto dissolve it so that the tracer may be desorbed.

Suitable derivatizing reagents to react with the non-halogenated tracersinclude, but are not necessarily limited to, any reagent that can attachat least one halogen atom to the non-halogenated tracer. Non-limitingexamples include, but are not necessarily limited to, pentafluoro benzylchloride, pentafluoro benzoyl bromide, pentafluoro phenyl hydrazine, tomake sensitive derivatives of compounds that may be used to determinethe presence of these compounds by gas chromatography with an electroncapture detector (GC/ECD). Other methods that attach halogens may alsobe used, such as trifluoro acetic anhydride mixed with trichloro ethanolto make esters. While the use of these derivatized tracers has beenknown, it has not been re-invented or applied to the production ofhydrocarbons until now. These compounds are known in other industriessuch as medicine or the environmental industry to measure these items atextremely low levels in other materials, but not used as tracers. It issurprising and unexpected to use these tracers in oilfield producedwater and/or oil, without the use of halogenated tracer compounds tobegin with. The method herein uses non-halogenated or halogen-freealcohols, ketones, and/or organic acids. The use of thesenon-halogenated molecules saves a large expense because the halogenatedcompounds are far more expensive (by orders of magnitude) than thecorresponding non-halogenated alcohols, ketones and/or organic acids.

Fluorinated benzoic acid has been used in the past as a tracer, wherebenzoic acid has been fluorinated prior to use. An important distinctionin the present method is that none of the compounds are fluorinated (orotherwise halogenated) until they come back to the surface and aretransported to a laboratory (stationary or mobile) for derivatization(reaction with a derivatizing agent such as pentafluoro benzyl chloride)and detection. While non-fluorinated benzoic acid or alkyl aromaticacids may be used in the present invention, if fluorinated derivativeswere made of those compounds, they would not be the same derivatives asthose used in the prior methods; they would be, e.g., a fluorinatedester of the benzoic acid (so two aromatic rings connected by an etherlinkage where one is fluorinated and the other is not).

One embodiment of a method of using the tracers as described herein isthat the non-halogenated tracers would be applied at a rate of about 10lbs per barrel (about 27 grams/liter) of a single tracer absorbed on asubstrate, such as SORB™ or MULTISORB™ scale inhibitors available fromBaker Hughes, into a single frac stage and then look for it to beproduced back. Every frac stage may have a different identifiablecompound in it or perhaps two tracer compounds; one that is oil solubleand one that is water soluble. Then, when the well is put back online, asample of the water and oil is sent to the laboratory for analysis. Inthe lab the sample is derivatized so that the compound may be detectedat the lowest detection level. The tracers may be derivatized withpentafluoro benzyl chloride or similar reagents to form the pentafluoroether, ester or hydrazine of the tracer compound for detection andanalysis by gas chromatography with an electron capture detector. Theacids may also be derivatized with reagents, such as trichloro ethanol,to make trichloro ethyl esters. Trifluoro acetic anhydride may be usedto make trifluoro derivatives. Other suitable derivatizing agentsinclude, but are not necessarily limited to, pentafluoro benzoylbromide, pentafluoro phenyl hydrazine and the like. Details aboutderivatizing the non-halogenated tracers may be found in Daniel P.Knapp, Handbook of Analytical Derivatization Reactions, John Wiley andSons, 1979, and Karl Blau and John Halket, Handbook of Derivatives forChromatography, John Wiley and Sons 1993, both of which are incorporatedby reference herein. It should be emphasized that the derivatizedtracers for chromatography in the method described herein are nothalogenated compounds to begin with. As a matter of fact, most of thederivatives discussed in both books have nothing to do with halogens.These references primarily describe methods to derivatize compounds forGC or HPLC analysis that are difficult to analyze by chromatography bythemselves.

From this procedure it may be determined which frac stage is producingthe water and which frac stage is producing the oil. A broad detectionrange would be a detection of hundreds of mg/L of the compounds to aslow as about 0.02 mg/L of the tracers. The detection level would bedependent on the amount of produced water and the total flow rates ofoil and water from the well.

The chemical reaction schemes shown below describe these derivatizationreactions, for example, in the case of an aliphatic alcohol (I), analiphatic acid (II) and an aliphatic ketone (III) where n=7-27. Thederivatives may be formed as follows, pentafluorophenyl ester of thealiphatic acid (IV), pentafluorobenzyl ester of aliphatic acid (V),2,2,2-trichloroethylester of aliphatic acid (VI) andpentafluorophenylhydrazone of aliphatic ketone (VII).

The invention will now be described with respect to particularembodiments of the invention which are not intended to limit theinvention in any way, but which are simply to further highlight orillustrate the invention.

Experimental

The following aliphatic alcohols have been tested to detection limits of0.02-0.03 mg/L: C10, C12, C13 (2-tridecanol), C14, C15, C16, C18 (withan unsaturation in the #9 position). The following aliphatic organicacids at 190-400 mg/L have also been tested, but the results were offscale and thus they could be diluted many orders of magnitude and stillbe expected to be effective: C8, C10, C12, C14, C7, C18. The organicacids (i.e. carboxylic acids) were tested as their trichloroethyl esterderivatives. It is thus expected that any alcohols, ketones, and/ororganic acids will work regardless of whether they are aliphaticstraight chains, branched chains, whether they contain unsaturation oreven have aromatic rings or saturated rings structures. It is expectedthat corresponding ketones should work as well.

While one concern is that there may be naturally occurring compoundspresent in crude oils that would interfere with the analysis of thetracers, three different blank crudes have been analyzed usingderivatized tracers and it has been determined that none of them wouldhave interfered with the analysis.

The difference in analytical results of the chromatograms between ablank crude and a sample containing the derivatized alcohol tracers isdramatic. A crude oil with a C15 alcohol added may be used as aninternal standard. Internal standards are used to show that the responsein crude oil is essentially the same as the standard. The chromatogramis a relatively smooth curve with a spike for the C15 alcohol. Achromatogram of a sample with seven alcohols from C10 to C18 and thesame C15 internal standard shows a noticeable peak for each alcohol inthe relatively smooth curve giving a very remarkable contrast. Thechromatogram of the alcohol standard showing that the C15 internalstandard has a peak height of 1899 Hz while the same internal standardin a crude oil has a peak height of 1341 Hz. Thus, if derivatizedalcohols were in the crude oil, they would be seen.

Tracer Returns Study

Shown in FIG. 1 is a graph of the returns of a 2% solution of 5halogenated tracers from TRACERCO on diatomaceous earth (DE). Thesamples were put onto the DE and then washed off with successive columnvolumes of ISOPAR “L”. ISOPAR “L” is a pure alkyl hydrocarbon used tosimulate crude oil in the laboratory. What is seen is that thehalogenated tracers come off the DE right away and go to zero detectionalmost immediately. Thus, from a field detection standpoint, if one doesnot catch the sample right away, it will be lost. In fact, it is readilyseen that Tracer B came back so quickly, it was almost not found.

In contrast to the FIG. 1 data, the FIG. 2 graph shows data generatedfrom a 1% loading of alcohols on DE (half as much loading as for FIG.1). The sample was washed with the same ISOPAR to simulate crude oil andthe alcohol(s) content was measured in the return fluids with porevolume returns. What was seen was that the alcohols came off the DE muchmore slowly and in a more predictable manner for a longer period of timethan the halogenated tracers of FIG. 1. This allows for a longer testingperiod and more useful data.

It should be noted that the Y axis for the two graphs of FIGS. 1 and 2are slightly different. The Y axis for FIG. 1 is mg/L and the Y axis forFIG. 2 is as a % of the sample put on the DE. This is because the amountof each alcohol put on the column was slightly different and theexperimenters wanted to compare them to each other for returnproperties. Actual returns were from a 60 mg/L to 30 mg/L for the firstpore volumes to a low of 16.8 mg/L to 2.8 mg/L at 100 pore volumes forFIG. 2. If FIG. 1 was compared in the same way, the first sample pointwould be at 10% and go to zero by the second sample point. The realproblem is that the halogenated tracers do not “stick” or absorb intoand/or adsorb onto the DE to begin with. In contrast, the alcohols,acids and ketones of the method described herein will “stick” (absorbinto and/or adsorb onto) to the DE and come off of it slower.

It is to be understood that the invention is not limited to the exactdetails of procedures, operation, exact materials, or embodiments shownand described, as modifications and equivalents will be apparent to oneskilled in the art. Accordingly, the invention is therefore to belimited only by the spirit and scope of the appended claims. Further,the specification is to be regarded in an illustrative rather than arestrictive sense. For example, specific combinations of non-halogenatedtracers, derivatizing agents, substrates, derivatized agents, fracturingstages used, derivatizing reaction conditions, but not specificallyidentified or tried in a particular method, are anticipated to be withinthe scope of this invention.

The terms “comprises” and “comprising” in the claims should beinterpreted to mean including, but not limited to, the recited elements.

The present invention may suitably comprise, consist of or consistessentially of the elements disclosed and may be practiced in theabsence of an element not disclosed. For instance, there may be provideda method for determining the presence of a derivatized tracer from asubterranean location that consists essentially of or consists ofintroducing at least one non-halogenated tracer into a subterraneanlocation, where the at least one non-halogenated tracer is a moleculehaving from 10 to 30 carbon atoms selected from the group consisting ofaliphatic, aromatic, saturated, unsaturated, and/or combinationsthereof, of alcohols, ketones, organic acids, organic acid salts,sulfonated alcohols, sulfonated ketones, sulfonated organic acids,sulfonated organic acid salts, and combinations thereof, where thenon-halogenated tracer is absorbed into and/or adsorbed onto a pluralityof substrates; recovering a fluid from the subterranean location wherethe fluid comprises the at least one non-halogenated tracer that hasdesorbed from the substrate, where a majority of the plurality of thesubstrates remains within the subterranean location; reacting the atleast one non-halogenated tracer at the subterranean location with areagent to give at least one derivatized tracer; and detecting the atleast one derivatized tracer from at least a portion of the recoveredfluid.

What is claimed is:
 1. A method for determining the presence of a tracerfrom a subterranean location comprising: introducing at least onenon-halogenated tracer into a subterranean location, where the at leastone non-halogenated tracer is a molecule having from 10 to 30 carbonatoms selected from the group consisting of aliphatic, aromatic,saturated, unsaturated, and/or combinations thereof, of alcohols,ketones, organic acids, organic acid salts, sulfonated alcohols,sulfonated ketones, sulfonated organic acids, sulfonated organic acidsalts, and combinations thereof, where the non-halogenated tracer isabsorbed into and/or adsorbed onto a plurality of substrates; recoveringa fluid from the subterranean location where the fluid comprises the atleast one non-halogenated tracer that has desorbed from the substrate,where a majority of the plurality of the substrates remains within thesubterranean location; reacting the at least one non-halogenated tracerwith a reagent to give at least one derivatized tracer; and detectingthe at least one derivatized tracer from at least a portion of therecovered fluid.
 2. The method of claim 1 where the reagent is a reagentthat can attach at least one halogen atom to the non-halogenated tracer.3. The method of claim 2 where the reagent is selected from the groupconsisting of pentafluoro benzyl chloride, pentafluoro benzoyl bromide,pentafluoro phenyl hydrazine, trifluoro acetic anhydride, trichloroethanol, and combinations thereof.
 4. The method of claim 1 where theamount of at least one derivatized tracer in the at least a portion ofthe recovered fluid is 0.02 mg/L or more.
 5. The method of claim 1 wherethe fluid is selected from the group consisting of oil, water andcombinations thereof.
 6. The method of claim 1 where the at least onederivatized tracer is detected using a method selected from the groupconsisting of a gas chromatograph with an electron capture detector, agas chromatograph with a mass spectrometer, high performance liquidchromatography with a mass spectrometer, and combinations thereof. 7.The method of claim 1 where: the introducing comprises: introducing afirst non-halogenated tracer absorbed into and/or absorbed onto a firstplurality of substrates into a first subterranean location in a firstfracturing stage; introducing a second non-halogenated tracer absorbedinto and/or absorbed onto a second plurality of substrates differentfrom the first non-halogenated tracer and different from the firstplurality of substrates, respectively, into a second subterraneanlocation in a second fracturing stage different from the first stage;recovering a first fluid containing the first non-halogenated tracerfrom the first subterranean location and recovering a second fluidcontaining the second non-halogenated tracer from the secondsubterranean location, where the respective tracers have desorbed fromtheir respective substrates; and the reacting comprises: reacting thefirst non-halogenated tracer with a reagent to give a first derivatizedtracer, and reacting the second non-halogenated tracer with a reagent togive a second derivatized tracer different from the first derivatizedtracer; detecting and distinguishing the fluid containing the firstderivatized tracer and the fluid containing the second derivatizedtracer.
 8. The method of claim 1 where the substrate comprises amaterial selected from the group consisting of diatomaceous earth,alumina, an absorbent polymer, silica particulate, precipitated silica,activated carbon, zeolite, fullers earth, organic synthetic highmolecular weight water-insoluble adsorbants, and combinations thereof.9. The method of claim 1 where the substrate is a proppant.
 10. A methodfor determining the presence of a tracer from a subterranean locationcomprising: introducing at least one non-halogenated tracer into asubterranean location, where the at least one non-halogenated tracer isa molecule having from 10 to 30 carbon atoms selected from the groupconsisting of aliphatic, aromatic, saturated, unsaturated, and/orcombinations thereof, of alcohols, ketones, organic acids, organic acidsalts, sulfonated alcohols, sulfonated ketones, sulfonated organicacids, sulfonated organic acid salts, and combinations thereof, wherethe non-halogenated tracer is absorbed into and/or adsorbed onto aplurality of substrates; recovering a fluid from the subterraneanlocation where the fluid comprises the at least one non-halogenatedtracer that has desorbed from the substrate, where a majority of theplurality of the substrates remains within the subterranean location,where the fluid is selected from the group consisting of oil, water andcombinations thereof; reacting the at least one non-halogenated tracerwith a reagent to give at least one derivatized tracer, where thereagent is one that can attach at least one halogen atom to thenon-halogenated tracer; detecting the at least one derivatized tracerfrom at least a portion of the recovered fluid.
 11. The method of claim10 where the reagent is selected from the group consisting ofpentafluoro benzyl chloride, pentafluoro benzoyl bromide, pentafluorophenyl hydrazine, trifluoro acetic anhydride, trichloro ethanol andcombinations thereof.
 12. The method of claim 10 where the amount of atleast one derivatized tracer in the at least a portion of the recoveredfluid is 0.02 mg/L or more.
 13. The method of claim 10 where the atleast one derivatized tracer is detected using a method selected fromthe group consisting of a gas chromatograph with an electron capturedetector, a gas chromatograph with a mass spectrometer, high performanceliquid chromatography with a mass spectrometer, and combinationsthereof.
 14. The method of claim 10 where: the introducing comprises:introducing a first non-halogenated tracer absorbed onto and/or adsorbedonto a first plurality of substrates into a first subterranean locationin a first fracturing stage; introducing a second non-halogenated tracerabsorbed into and/or adsorbed onto a second plurality of substratesdifferent from the first non-halogenated tracer and different from thefirst plurality of substrates, respectively, into a second subterraneanlocation in a second fracturing stage different from the first stage;recovering a first fluid containing the first non-halogenated tracerfrom the first subterranean location and recovering a second fluidcontaining the second non-halogenated tracer from the secondsubterranean location, where the respective tracers have desorbed fromtheir respective substrates; the reacting comprises: reacting the firstnon-halogenated tracer with a reagent to give a first derivatized tracerand reacting the second non-halogenated tracer with a reagent to give asecond derivatized tracer different from the first derivatized tracer;detecting and distinguishing the fluid containing the first derivatizedtracer and the fluid containing the second derivatized tracer.
 15. Themethod of claim 10 where the substrate comprises a material selectedfrom the group consisting of diatomaceous earth, alumina, an absorbentpolymer, silica particulate, precipitated silica, activated carbon,zeolite, fullers earth, organic synthetic high molecular weightwater-insoluble adsorbants, and combinations thereof.
 16. The method ofclaim 10 where the substrate is a proppant.
 17. A method for determiningthe presence of a tracer from a subterranean location comprising:introducing at least one non-halogenated tracer into a subterraneanlocation, where the at least one non-halogenated tracer is a moleculehaving from 10 to 30 carbon atoms selected from the group consisting ofaliphatic, aromatic, saturated, unsaturated, and/or combinationsthereof, of alcohols, ketones, organic acids, organic acid salts,sulfonated alcohols, sulfonated ketones, sulfonated organic acids,sulfonated organic acid salts, and combinations thereof, where thenon-halogenated tracer is absorbed into and/or adsorbed onto a pluralityof substrates; recovering a fluid from the subterranean location wherethe fluid comprises the at least one non-halogenated tracer that hasdesorbed from the substrate, where a majority of the plurality of thesubstrates remains within the subterranean location, where the fluid isselected from the group consisting of oil, water and combinationsthereof, where the amount of at least one derivatized tracer in the atleast a portion of the recovered fluid is 0.02 mg/L or more; reactingthe at least one non-halogenated tracer with a reagent to give at leastone derivatized tracer, where the reagent is selected from the groupconsisting of pentafluoro benzyl chloride, pentafluoro benzoyl bromide,pentafluoro phenyl hydrazine, trifluoro acetic anhydride, trichloroethanol, and combinations thereof; and detecting the at least onederivatized tracer from at least a portion of the recovered fluid usinga method selected from the group consisting of a gas chromatograph andan electron capture detector, a gas chromatograph with a massspectrometer, high performance liquid chromatography with a massspectrometer, and combinations thereof.
 18. The method of claim 17where: the introducing comprises: introducing a first non-halogenatedtracer absorbed onto and/or adsorbed onto a first plurality ofsubstrates into a first subterranean location in a first fracturingstage; introducing a second non-halogenated tracer absorbed into and/oradsorbed onto a second plurality of substrates different from the firstnon-halogenated tracer and different from the first plurality ofsubstrates, respectively, into a second subterranean location in asecond fracturing stage different from the first stage; recovering afirst fluid containing the first non-halogenated tracer from the firstsubterranean location and recovering a second fluid containing thesecond non-halogenated tracer from the second subterranean location,where the respective tracers have desorbed from their respectivesubstrates; and the reacting comprises: reacting the firstnon-halogenated tracer with a reagent to give a first derivatized tracerand reacting the second non-halogenated tracer with a reagent to give asecond derivatized tracer different from the first derivatized tracer;detecting and distinguishing the fluid containing the first derivatizedtracer and the fluid containing the second derivatized tracer.
 19. Themethod of claim 17 where the substrate comprises a material selectedfrom the group consisting of diatomaceous earth, alumina, an absorbentpolymer, silica particulate, precipitated silica, activated carbon,zeolite, fullers earth, organic synthetic high molecular weightwater-insoluble adsorbants, and combinations thereof.
 20. The method ofclaim 17 where the substrate is a proppant.